title: POP-pincer silyl complexes of group 9: rhodium versus iridium.
abstract: 9,9-Dimethyl-4,5-bis(diisopropylphosphino)xanthene (xant(P(i)Pr2)2) derivatives RhCl{xant(P(i)Pr2)2} (1) and I rHCl{xant(P(i)Pr2)[(i)PrPCH(Me) CH2]} (2) react with diphenylsilane and triethylsilane to give the saturated d(6)-compounds RhHCl(SiR3){xant(P(i)Pr2)2} (SiR3 = SiHPh2 (3), SiEt3 (4)) and IrHCl(SiR3){xant(P(i)Pr2)2} (SiR3 = SiHPh2 (5), SiEt3 (6)). Complexes 3 and 5 undergo a Cl/H position exchange process via the MH{xant(P(i)Pr2)2} (M = Rh (8), Ir (E)) intermediates. The rhodium complex 3 affords the square planar d(8)-silyl derivative Rh(SiClPh2){xant(P(i)Pr2)2} (7), whereas the iridium derivative 5 gives IrH2(SiClPh2){xant(P(i)Pr2)2} (9), which is stable. In agreement with the formation of 7, the reactions of 8 with silanes are a general method to prepare square planar d(8)-rhodium-silyl derivatives. Thus, the addition of triethylsilane and triphenylsilane to 8 initially leads to the dihydrides RhH2(SiR3){xant(P(i)Pr2)2} (SiR3 = SiEt3 (10), SiPh3 (11)), which lose molecular hydrogen to afford Rh(SiR3){xant(P(i)Pr2)2} (SiR3 = SiEt3 (12), SiPh3 (13)). Treatment of 7 with NaBAr(F)4·2H2O leads to the cationic five-coordinate d(6)-species [RhH{Si(OH)Ph2}{xant(P(i)Pr2)2}]BAr(F)4 (14) through a silylene intermediate. According to the participation of the latter in the formation of 14, this cation is an efficient catalyst precursor for the monoalcoholysis of diphenylsilane with a wide range of alcohols, reaching turnover frequencies at 50% of conversion between 4000 and 76 500 h(-1). The X-ray structures of 3, 6, 7, 9, 12, and 14 are also reported.
authors.affiliation: Departamento de Química Inorgánica, Instituto de Síntesis Química y Catálisis Homogénea (ISQCH) , Universidad de Zaragoza - CSIC , 50009 Zaragoza, Spain.
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Esteruelas
authors.forename: Montserrat
authors.initials: M
authors.lastname: Oliván
authors.forename: Andrea
authors.initials: A
authors.lastname: Vélez